1. Field of the Invention
This invention relates to an auger for agricultural mixers, specifically feed mixers having augers that are substantially perpendicular to a plane of a floor.
2. Background of the Invention
Agricultural mixers are used for mixing feed materials such as hay, silage and other nutrients including animal feed supplements and grains. These feed materials are then discharged and fed to various livestock such as cattle and dairy cows. Sometimes the mixing of such feed includes depositing a whole round or square bale of hay into the mixer. The mixer then cuts and processes the bale into the desired consistency before and during the mixing of the other feed nutrients.
In known mixers, there are many different configurations including horizontal augers, reel type arrangements, and vertical augers. In the vertical auger type mixers, the auger and container body designs are generally similar. The container body includes a horizontal floor, which closely approximates the diameter of the vertical auger at its base. Walls extend upward from the floor to form a container with an open top, so that feed materials can be loaded from above.
The walls of the container are in the shape of an inverted frustum, being wider at the top and narrower at the base. However, the walls on the sides of the container are typically arranged at a steeper angle in comparison to the walls on the ends of the container. The reasons for this shape in vertical mixers is both to narrow the overall profile of the container, and to facilitate feed processing inside the mixer. A similar shape is utilized in the case of multiple auger mixers, with the frustum shape being stretched to accommodate the additional augers.
The oblong shape of the vertical mixer container at the top edge, combined with the cone shape of the auger, creates a wide cavity for the reception of feed at the ends of the container, and a somewhat narrower cavity at the sides of the container. During the mixing of feed inside the container, the auger rotates at a constant speed around a vertical axis of rotation, urging the feed materials around the inside circumference of the container. When the feed encounters the narrower cavities at the sides, a restriction point is created, thus forcing a mixing action as well as allowing the auger knives to further cut or process the feed materials. As the feed moves into the wider cavities at the ends of the container, the feed increases in velocity and falls down into the cavity. The resulting rotary motion of the feed is that of alternating restriction and release, slow and fast, rising and falling movement, which causes the mixing and processing of the materials.
The auger design generally consists of a center core on a vertical axis of rotation, with helical auger flighting wrapped around this core. The auger flighting has an overall conical appearance, being wider at the base and narrower at the top. The auger can be described as having a lower core and flighting segment and an upper core and flighting segment. The leading edge of the lower flighting segment extends on a radius from the axis of rotation to closely match the diameter of the floor at the base of the container, in order to engage substantially all the feed material at the floor. The radius distance from the axis of rotation to the outer edge of the lower flighting segment gradually gets shorter as it gets further from the leading edge, generally in the first revolution or “pitch” of the lower flighting segment. Thus, the lower flighting tapers from the bottom toward the top, being wider at the leading edge and narrower at the trailing edge. The trailing edge of the lower flighting segment is positioned adjacent to the leading edge of the upper flighting segment.
The upper flighting segment has a relatively constant radius distance from the axis of rotation to the outer edge of the upper flighting segment, although some taper toward the top of the auger is sometimes utilized. Knives are added to the flighting to help cut and process the feed materials. The flighting segments can also consist of individual paddles or short flighting sections oriented in a helical pattern to urge the material in the desired direction.
A discharge opening is typically located at the lower edge of the container wall to discharge the feed materials after mixing. A door is positioned adjacent to the discharge opening for controlling the flow of feed materials when discharging.
In vertical mixers of typical configuration with augers which are concentric on the axis of rotation, one disadvantage is that in order to facilitate hay processing, the sides must be narrowed to restrict the feed movement adjacent to the auger, thus allowing the knives to process the hay. This narrow gap between the auger flighting and the enclosure at both sides will not allow large bales to fall down further into the mixer at the sides, and thus limits the mixing ability of the apparatus.
Another disadvantage of a concentric auger is that the top of the upper core does not move relative to the enclosure, and thus bales can sit on top of the upper core and fail to descend further into the enclosure.
Another disadvantage of a concentric auger is that the auger flighting remains flat during its movement around the axis of rotation, allowing feed materials to accumulate on top of the flighting even after the discharge of the feed materials.
Another disadvantage of a concentric auger is that the required narrow gaps at the sides reduce the overall volumetric capacity of the mixer enclosure.
Another disadvantage of a concentric auger is that the required narrow gaps at the sides cause materials to spill over both sides, resulting in loss of feed materials.
Another disadvantage of a concentric auger is that additional horsepower is required for the auger knives to cut and process the feed materials on both restrictive sides of the container at the same time.